Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $111.38   7.679%   $119.9329   $119.93   $119.95   $119.90  
  Purchase #2 $120.27   13.345%   $136.32   $136.32   $136.30   $136.30  
  Purchase #3 $88.92   6.818%   $94.9826   $94.98   $95.00   $95.00  
  Purchase #4 $203.69   12.593%   $229.3407   $229.34   $229.35   $229.30  
  Purchase #5 $28.79   9.739%   $31.5939   $31.59   $31.60   $31.60  
  Purchase #6 $184.80   11.216%   $205.5272   $205.53   $205.55   $205.50  
  Purchase #7 $228.67   9.589%   $250.5972   $250.60   $250.60   $250.60  
  7 purchase totals = $966.52       $1,068.2945   $1,068.29   $1,068.35   $1,068.20